The Burakovka layered pluton of basic and mafic rocks is the largest intrusive massif in the Baltic Province composed of Si- and Mg-rich boninite-like rocks. The pluton consists of two individual bodies, each having its own internal structure, and contacting each other in their apical parts, known as the Aganozero and Shalozero-Burakovka bodies. Both bodies have a similar rock sequence including five differentiated zones upward: mafic rocks, pyroxenite, gabbro norite, pigeonite gabbro norite, and magnetite gabbro diorite the latter found only in the Shalozero-Burakovka Body. Being generally similar to each other, these bodies differ notably in the styles of their cumulate stratigraphy and, to a lesser extent, in composition. The pluton is distinguished by the presence of markers - singular interlayers of high-temperature mafic cumulates emplaced in the sequence of lower-T formations. Their origin is believed to have been associated with the intrusion of fresh magma portions into the crystallizing magma chambers. The same mechanism is believed to have been responsible for a macrorhythmic pattern found in the southeastern portion of the Shalozero-Burakovka intrusive body. Using chemical and mineralogical data, it is shown that the bodies discussed were derived from similar high-Si and high-Mg magmas, except that the Aganozero Body was emplaced 50 million years later than the Shalozero-Burakovka intrusion: the former was dated Sm-Nd isochron 2372 22 Ma e Nd=-3.220.13, and the latter, 2433 28Ma eNd=-3.14 0.14. It is concluded that the Burakovka Pluton was a long-lived magma center which developed above a local mantle plume, the origin of which had been associated with the activity of a megaplume which had been responsible for the existence of the Baltic province throughout a period of 200 million years.
petrology, Paleoproterozoic layered pluton, mafic rocks.
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